Bloat is not defined by core OS apps regardless of whether we use them or not. Bloat ware is the supplemental applications that a carrier or other third party installs on top of the core package.
Whilst you may find stock apps that you don't use 'bloat' that ultimately is not what is being referred to.
bloatware
ˈbləʊtwɛː/
nounCOMPUTINGinformal
software whose usefulness is reduced because of the excessive disk space and memory it requires.
"a nasty piece of cross-platform bloatware that's in serious need of a total overhaul"
unwanted software included on a new computer or mobile device by the manufacturer.
"users must initially contend with the usual bevy of bloatware (unnecessary toolbars, games of questionable value)"